• Simulations explain Greenland's slower s

    From ScienceDaily@1:317/3 to All on Wednesday, April 06, 2022 22:30:40
    Simulations explain Greenland's slower summer warming

    Date:
    April 6, 2022
    Source:
    Hokkaido University
    Summary:
    Climate changes in the tropical Pacific have temporarily put the
    brakes on rapid warming and ice melting in Greenland.



    FULL STORY ========================================================================== Climate changes in the tropical Pacific have temporarily put the brakes
    on rapid warming and ice melting in Greenland.


    ==========================================================================
    A puzzling, decade-long slowdown in summer warming across Greenland has
    been explained by researchers at Hokkaido University in Japan. Their observational analysis and computer simulations revealed that changes in
    sea surface temperature in the tropical Pacific Ocean, thousands of miles
    to the south, trigger cooler summer temperatures across Greenland. The
    results, published in the journal Communications Earth & Environment,
    will help improve future predictions of Greenland ice sheet and Arctic
    sea ice melting in coming decades.

    "The Greenland ice sheet is melting in the long run due to global warming associated with greenhouse gas emissions, but the pace of that melting
    has slowed in the last decade," says Hokkaido University environmental
    Earth scientist, Shinji Matsumura. "That slowing was a mystery until our research showed it is connected to changes to the El Nin~o climate pattern
    in the Pacific." El Nin~o is a natural, cyclic phenomenon that raises
    the water temperature in the central and east-central equatorial Pacific
    Ocean. Scientists know that such large-scale changes alter atmospheric conditions elsewhere due to their association with powerful waves of
    air pressure called teleconnections. But climate experts struggled to
    see how the Pacific El Nin~o could cool Greenland in the summer, because easterly summer winds in the tropics usually prevent such teleconnections
    from forming.

    In the new study, the team accounted for recent changes in the Pacific
    El Nin~o event, which pushed the warmer sea temperatures further north
    than usual. This took them beyond the influence of the easterly wind and allowed atmospheric teleconnections that stretch up to Greenland to form.

    In turn, these teleconnections disrupt the atmospheric conditions and
    thus the weather around Greenland in the summertime. Specifically, they
    drive more intense cyclones, which move colder air over the land. This
    is enough, the new study shows, to explain the lower-than-expected
    temperatures and ice melting in the region. Temperatures and rates of
    ice sheet melting both peaked in 2012.

    "The findings, and the slowdown in Greenland's summertime warming, do
    not undermine the seriousness of climate change or the need to tackle greenhouse gas emissions," Matsumura stresses. Rather, they demonstrate
    how natural changes can act alongside the long-term global warming
    trend to vary local conditions. The slowdown in warming is local to
    Greenland. The wider Arctic region remains one of the fastest warming
    places on Earth.

    El Nin~o events tend to be followed by similar but different natural
    climatic shifts called La Nin~a, in which sea surface temperatures
    drop. These events tend to bring higher temperatures to Greenland.

    "We expect that global warming and ice sheet melting in Greenland and
    the rest of the Arctic will accelerate even further in the future due
    to the effects of anthropogenic warming," Matsumura says.


    ========================================================================== Story Source: Materials provided by Hokkaido_University. Note: Content
    may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Shinji Matsumura, Koji Yamazaki, Kazuyoshi Suzuki. Slow-down
    in summer
    warming over Greenland in the past decade linked to central Pacific
    El Nin~o. Communications Earth & Environment, 2021; 2 (1) DOI:
    10.1038/ s43247-021-00329-x ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220406101726.htm

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